I have a renault Clio,2010 plates 25000 miles to date. I bought this car about three years ago and have had no problems except a new coil pack which I believe is a common fault with these cars. I had it serviced? about 15 months ago oil change filters etc and all seems to be fine. Today I decided to lift the bonnet to remind me where the engine was because it runs so quietly. Anyway everything appeared to be in order, battery- cooling system levels ok I checked the oil level and it was as it should have been but a bit "cleaner"than I would have thought,then I checked the oil filler cap and found it had a slight smearing of sludge around the neck; in older older cars this usually denoted a gasket leakage or such but I didn't happen much now. Some "friends" say it is just the residue left from synthetic oils. Whatever it is I would appreciate your replies Thanks for putting up with me.S.O.G
The most likely cause is the low mileage the car has covered. If it is only used for short journeys the engine will not be achieving operating temperature for long enough to dispel the residue. Change the oil annually and follow manufacturers guide for oil type and you should be ok